Continuous rotary electrostatographic apparatus



May 6, 1969 s T ET AL 3,442,585

CONTINUOUS ROTARY ELECTROSTATOGRAPHIG APPARATUS Sheet Z of 4 Filed Oct. 25, 1965 Len d9. 'T (0d Zier May 6, 1969 3,442,585

CONTINUOUS ROTARY ELECTROSTATOGRAPHIC APPARATUS L. A. SMITZER ET AL Sheet & of 4 Filed Oct. 23, 1965 2 2 @w fi MQ fl e 9 F L [s M y mlww By 4% m,

May 6 1969 SNHTZER ET AL 3,442,585

CONTINUOUS ROTARY ELECTROSTATOGRAPHIC APPARATUS Filed Oct. 25, 1965 Sheet 3 01"4 May G, 1969 SMlTZER ET AL 3,442,585

CONTINUOUS ROTARY ELECTROSTATOGRAPHIC APPARATUS Sheet Filed Oct. 25, 1965 wuenfqr-s law's/R577?! Zen /'7. Tyle alter f uzes William 586x175 W fiz K110 .731

United States Patent 3,442,585 CONTINUOUS ROTARY ELECTROSTATOGRAPHIC APPARATUS Louis A. Smitzer, Chicago, Len A. Tyler, Evanston, Walter Hines, Roselle, and William E. Bixby, Deerfield, Ill., assignors to Bell & Howell Company, Chicago Ill., a corporation of Illinois lFiled Oct. 23, 1965, Ser. No. 503,654 Int. Cl. G03g 15/04 US. Cl. 355-3 6 Claims This invention relates generally to the art of electrostatography and more specifically relates to a method and apparatus for making microimages electrostatographically wherein a photo-conductive surface is moved in the direction of its length through successive stations of charging, exposing and developing and simultaneously therewith a development electrode at the development station is reciprocated in a direction transverse to the direction of movement of the photo-conductive surface. Thus, if the photo-conductive surface is on a drum, brushes on opposite sides of the drum and turned separately operate to continuously scrub the electrode surfaces. Both the drum and the electrode are mounted on means insuring concentricity of the photo-conductive surface relative to the drum axis and in order to maintain a clearance between the photo-conductive surface and the electrode at an optimum spacing dimension.

In accordance with prior art teachings, microimages have been successively reproduced electrostatographical'ly only in apparatus which operates in a planetary mode, Le, a single image is successively cycled through the successive steps of charging, exposing and developing. Thus, it is an object of the present invention to provide a method and apparatus wherein microimages may be reproduced electrostatographically continuously so that the micro' images may be recorded on a continuous strip of film.

Because microimagery contemplates size reduction in the order of 10X to 44X, a particularly critical factor in producing a successful electrostatographic apparatus and method resides in the development of a visible utilitarian image having the requisite characteristics of resolution and definition and which is of uniform density without tears and streaks.

The minute nature of the microimage requires utilization of special development materials which will lend themselves to the formation of an image having the foregoing characteristics. Thus, a very finely divided material such as comminuted carbon particles will make a satisfactory microimage, however, it is a particular object of the present invention to provide a method and apparatus for handling such a development material in a continuous rotary machine so that consistently reliable results can be expected.

In accordance with the principles of the present invention, a development unit is provided featuring the use of a transversely slidable electrode which is reciprocated transversely with respect to the direction of movement of the photo-conductive surface. Thus, brushes on opposite sides of the drum carrying the photo-conductive surface and turned separately from the drum operate to continuously scrub the electrode surface and keep the electrode surface free of developer particles.

Moreover, it is contemplated by the present invention that the development unit electrode be maintained at an optimum spacing dimension which may be within limits of approximately 50 to 500 microns. The electrode frame is carried on an adjustable micrometer sling so that the electrode can be adjustably spaced 'With respect to the photo-conductive surface of the drum.

Further, in order to keep the spacing gap between the development electrode and the drum at an optimum Patented May 6, 1969 ice dimension, the drum mounting has to be perfectly concentric and it is thus contemplated by the present invention that the drum and its mount use a cone and a correspondingly cone-shaped recess, thereby to provide a selfcentering mount which will locate and maintain the drum in almost perfect concentricity when it is clamped onto its driving shaft.

The drum of the present invention is also characterized by the provision of insulative material forming side seals and located to give more uniform charging to the edges of the drum, thereby improving the capability of the drum of receiving and holding a uniform charge on the photoconductive surface and also the side seals develop an improved sealing action for confining the developer material in the area of the development electrode.

It is therefore an object of the present invention to provide a method and apparatus for effecting a continuous reproduction of microimages.

Yet another object of the present invention is to provide a continuous rotary electrostatographic apparatus having improved development means.

Another object of the present invention is to provide in an electrostatographic apparatus a reciprocable electrode wherein the electrode moves transversely of the direction in which a photo-conductive surface is being moved.

Yet another object of the present invention is to provide an adjustable micrometer sling for an electrode in an electrostatographic machine whereby the spacing dimension between the electrode and the photo-conductive surface may be adjusted and maintained within an optimum range of spacing dimension.

A further object of the present invention is to provide a mounting means including a self-centering cone arrangement so that the spacing gap between a development electrode and a photo-conductive drum may be controlled by mounting the drum with optimum concentricity relative to its rotating driveshaft.

Another object of the present invention is to provide a sliding electrode and cleaning brushes on opposite sides of the drum so that the electrode surface will be constantly scrubbed by the brushes when the electrode is reciprocated during operation of the machine.

Still another object of the present invention is to provide side seals for a rotary photo-conductive drum for improving the capability of the drum to receive and maintain a uniform charge on its peripheral surface.

A still further object of the present invention is to provide a rotary drum with a peripheral photo-conductive surface and having side seals to afford an improved sealing action for confining developer material in a development electrode area at the developer station.

Many other features, advantages and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying sheets of drawings in which a preferred structural embodiment of the present invention is shown by way of illustrative example and from an understanding of which the improved methods of the present invention will also be understood.

On the drawings:

FIGURE 1 is a cross-sectional view showing an electrostatographic apparatus embodying the principles of the present invention and capable of practicing the methods contemplated hereby;

FIGURE 2 is a cross-sectional view taken generally on line II--II of FIGURE 1;

FIGURE 3 is a cross-sectional view taken on line III-III of FIGURE 2;

FIGURE 4 is a cross-sectional view taken on line 1V-IV of FIGURE 3;

' FIGURE is a cross-sectional view taken on line VV of FIGURE 2;

FIGURE 6 illustrates additional details of the drive;

FIGURE 7 is a cross-sectional view taken on line VII-VII of FIGURE 4; and

FIGURE 8 is a cross-sectional view taken on line VIII-VIII of FIGURE 1.

As shown on the drawings: As shown in FIGURE 1, an electrostatographic apparatus is designated generally at 10 and comprises a drum shown generally at 11 mounted for rotation on a shaft 12 and having a photoconductive surface 13 which constitutes a development surface and which is movable in the direction of its length upon rotation of the drum 11 in the direction of the arrow 14.

Outwardly adjacent the drum and specifically circumjacent the development surface 13 are spaced the various components which form stations for successively charging, exposing, developing and transferring an image on the photo-conductive surface 13". Thus, a charging station is established by a corona charging unit shown generally at 16 and which may constitute a corona charging unit known in the art as a Corotron. As the photo-conductive surface 13 is moved in proximity to the corona charging unit 16, a uniform charge is placed on the sur face.

The properly charged surface then moves to an exposure station which is established by an optical system shown generally at 17. The optical system 17 includes an adjustable lens 18 and a barrel 19 for transmitting a light image from material to be reproduced such as a document placed upon a rotatable drum in any manner such as is wellknown in the art, and illuminated by a light source including a pair of bulbs 20.

It will be understood that the photo-conductive surface 13 of the drum 11 is maintained in a light-proof enclosure 21 and, accordingly, the optical system 17 operates to project only the desired image against the photo-conductive surface 13, whereupon a latent electrostatographic image is formed in a well known manner.

The exposure station 17 is characterized by a lens system affording a desired image reduction. The amount of image reduction, of course, depends upon the optical characteristics of the optical system and reductions throughout commercial ranges are contemplated, for example, up to 44X. With the image carrier constituting 16 mm. film, a convenient reduction size would be approximately X.

In accordance with the principles of the present invention, a development unit is provided which is shown generally at 22 for the purpose of rendering the latent electrostatographic image on the photo-conductive surface 13 visible and utilitarian. The developed utilitarian image is then carried to a transfer station wherein a continuous strip of film such as 16 mm. roll film, shown at 23, is trained over a guide roller 24 carried in a slidable frame 26 actuated by a suitable shaft 27 associated with a motor 28 so that the film 23 may be engaged into effective transferred contact with the photo-conductive surface 13. It will be understood that the film is initially rolled on a storage roll 29 and is guided over suitable rollers 30 and through preconditioning means, if desired or necessary, to condition the surface of the film for receiving the transferred image. After transfer, the film is guided over other appropriate rolls 3 1 of a transport system and the film is taken up on a take-up roll 32 having a driven engagement with a sprocket wheel 33 rotatably driven through a gear train 34 in the direction of the arrows shown on the righthand side of FIGURE 1.

In order to condition the photo-conductive surface 13 for receiving a new image, a cleaning station is established by a brush mechanism shown generally at 36. The brush mechanism includes a shaft 37 to which is connected for co-rotation therewith a hub 38 having a bristle brush 39 on the outer periphery thereof. The shaft 37 is rotatably journalcd in a bearing support shown generally at 40 and the end of the shaft is connected to a pulley hub 41 over which is trained a pulley belt 42. The pulley belt 42 is also trained over a driving pulley 43 on the end of a drive shaft 44 rotatably driven by a motor 46.

The brush 38, 39 is enclosed by a housing 47 (FIGURE 8) and a tubular conduit 48 is connected to the housing, which conduit 48 is connected to a manifold 49 leading to a vacuum source 50 via a main conduit 51. Thus, any particulate development material removed from the photo-conductive surface 13 by the bristles 39 of the brush will be removed from the housing 47 to a recovery zone.

Referring now to FIGURE 2 in connection with FIG- URE 1, it will be noted that the shaft 12 is journaled for rotation in a bearing mounting indicated generally at 52 and a portion of the shaft projects in cantilever fashion outwardly of the bearing mounting 52 as indicated at 53.

Immediately outwardly adjacent the bearing mounting 52 is a bearing sleeve 54 which rotatably supports a hub member 56 of a first brush 57. The hub member 56 has an axially projecting flange 58 which is peripherally grooved at 59 thereby to track a pulley belt 60. The pulley belt 60 is also trained over a driving pulley 61 secured in co-rotatable assembly with a drive shaft 62 rotatably driven by a motor 63. Thus, the brush 57 can be rotated at a different rotational speed than the shaft 12.

Outwardly adjacent the bearing sleeve 54, the shaft 12 is provided with a circumferentially extending radially projecting abutment 64 providing a shoulder for a coneshaped centering sleeve 66. The cone-shaped sleeve 66 has an enlarged base 67 which abuts against the abutment 64 and has a peripheral tapered surface 68 converging towards a small end 69. The sleeve 66 is centrally bored as at 70 for receiving the end portion 53 of the shaft 12.

In order to insure perfect concentricity of the drum 11 on the shaft 12, the drum 11 is formed With a hub 71 having a center bore 72 characterized by a cone-shaped recess 73 generally complementary to the cone-shaped surface 68 of the sleeve 66. Thus, the drum 11 is assem bled to the shaft 12 by placing the same over the end portion 53 into mating engagement with the sleeve 66. A flanged washer 74 overlies the hub 71 at the edges of the bore 72 and a lock nut 76 is engaged with threads 77 formed on the end portion 53 of the shaft 12 so that the washer 74 may be drawn up to clamp the sleeve 66 and the hub 71 of the drum 11 into co-rotatable assembly with the shaft against the abutment 64.

Outwardly adjacent the threaded portion 77 of the end portion 53, the shaft 12 is characterized by a reduced diameter portion 78 on which is received a bearing sleeve 79. A hub 80 of a brush 81 is rotatably mounted on the bearing sleeve 79 and the hub 80 includes a flanged portion providing a recess 82 for accommodating the washer 74 and the lock nut 76. The hub is peripherally grooved as at 83 to track a pulley belt 84 which is trained over a driving hub 86 carried on a drive shaft 87 rotatably driven by the motor 63. Thus, the brush 81 like the brush 57 may be rotatably driven at a different speed than the rotational speed of the shaft 12 and the drum 11.

A lock nut 88 is engaged with the reduced Portion 78 of the shaft 12 and is suitably flanged to retain the bearing sleeve 79' and the brush 81 in place.

A housing enclosure 89 is provided for the brushes 57 and 81 and the interior of the housing enclosure is communicated with appropriate conduit means by the use of an L nipple connector on each side ofthe housing 89, the respective L connectors being identified at 90 and 91. A conduit 92 leads from the L connector 90 and a conduit 93 leads from the L connector 91 to a T connector 94. A conduit 96 extends from the T connector 94 to the manifold 49 so that any particulate material exhausted from the housing 89 will be directed to a recovery zone.

In order to rotatably drive the drum 11, the shaft 12 extends through an opening 97 formed in a frame member 98 and into the interior of a gear box 99.

The shaft 12 is connected to a motor 197 (FIGURE 6) by the components of a belt and pulley driving arrangement shown generally at 100 and 101 in FIGURE 2 and described more fully hereinafter in connection with FIG- URE 6.

It is also contemplated by the present invention that the hub 71 of the drum 11 be recessed in the side walls thereof, as shown in FIGURE 2 at 203 and 204, respectively. Each of the recesses 203 and 204 is generally annular and circumferentially continuous beginning at a radial shoulder portion 206 and extending to the outer periphery.

Received within each respective recess 203 and 204 is a seal ring identified at 207 and 208, respectively. The seal rings 207 and 208 constitute disks which may conveniently be made of plastic such as Lucite or impregnated fiber material. By providing seal rings 207 and 208 in the form of such insulative material, it will be appreciated that the rings function as side seals and form the side limits of the photo-conductive surface 13 on the'outer periphery of the drum 11. The photo-conductive surface may constitute any acceptable photo-conductive material such as selenium or the like and, thus, the insulative side seals formed by the rings 207 and 208 onrthe edges of the drum 11, improve the ability of the drum. to provide a uniform charge across the surface of the photo-conductive surface 13.

Furthermore, by providing the side seal disks or rings 207 and 208, the side seals may be positioned within 0.0005 inch of the adjoining electrode surface of the development unit 22, thereby affording an improved sealing action for confining developer material directed into a development electrode area for developing the microimages on the photo-conductive surface 13.

In order to retain the side seals 207 and 208 in firm assembly with the drum 11, a plurality of threaded apertures 209 may be formed at circumferentially spaced points in the drum and extending axially between the recesses 203 and 204. Headed bolts 210 may be utilized which are threaded into the apertures 209 and the heads of which are received in corresponding recesses formed in the rings 207 and 208.

Referring now to FIGURE 7 in conjunction with the other drawings, it will be noted that ,the development unit 22 forms a surface of curved configuration concentrically complementary to the development surface 13 provided by the photo-conductive layer on the drum 11. The curved surface of the development unit 22 is spaced from the surface 13 to form therewith a gap 115 of uniform width and thickness concentrically disposed with respect to the rotational axis of the drum 11. The periphery of the photoconductive surface 13 i salso' of a slightly smaller radius than that of the seal rings 207, 208 so as to allow the photoconductive surface 13 to be adjusted to its optimum spacing from an electrode 112, the optimum spacing being considerably greater than the preferred .0005 inch spacing of the seal rings, yet provide an effective seal to prevent particles of powder from escaping from the development zone thereth rough.

A fluid entry section is shown generally at 103 for interposing multiple fluid layers into the gap 115 while an electrode section 104 is provided for controlling the development field adjacent the drum 11. A vacuum pick-up section 105 is provided for picking up residual development powder. Each of the sections 103, 104, 105 extends through a selected number of degrees of are so that the total extent of the development unit 22 lies adjacent a substantial portion of the photo-conductive surface 13 on the drum 11.

As shown in FIGURE 7, the development unit 22 has a main body member 106 to which are connected supplemental body members 107 and 108 by means of a plurality of fastener bolts 109.

The main body member 106 has formed therein a dovetail guide or track 110 in which is slidably received a complementary shaped pilot portion 111 of the electrode 112. The oppositely disposed portion of the electrode 112 is curved to form the segment 104 of the curved surface and it will be understood that the electrode 112 may be connected to suitable control circuitry in order to produce a bias field to control the development field in the gap adjacent the photo-conductive surface 13.

Multiple fluid layers may be interposed in the gap at the fluid entry section 103 by virtue of the two separate channels formed between the components of the development unit 22 identified by the main body portion 106 and the supplemental body portions 107 and 108.

A powder cloud generator 113 (FIGURE 1) is connected by means of a conduit 116 to a nipple fitting 118 (FIGURE 7). A first fluid layer comprised of a development material dispersed in air is introduced from the powder cloud generator through the nipple fitting 118 into a channel 126 by means of an adapter 123 which threadedly engages the nipple 118. The actual discharge of powder-laden air from the nipple 118 occurs through an elongated tube shown at 124. In accordance with the present invention, the development material may constitute a development powder taking the form of particulated material such as carbon particles ground to a requisite degree of fineness. The particulate material entering the gap will be attracted to the charge pattern appearing on the photo-conductive surface 13 and will render such charge pattern visible as a developed microimage.

For the purpose of controlling the flow characteristics of the first fluid layer containing the development material, additional quantities of air may be introduced into the channel 126 through a conduit 1225 connected to a controlled source of compressed air 135.

A second fluid layer which comprises a stream of clean air is discharged into the gap 115 at a point which leads the discharge of the development powder, thereby increasing the pressure on the corresponding side of the gap and preventing the development powder from leaving the electrode area of the gap between the development unit 22 and the development surface 13. The same source of compressed air 135, referred to in the previous paragraph, may, by suitable valves (not shown), be used to supply the clean air to the channel 119 through a con duit 114 to a nipple fitting 117 and an adapter 120 which threadedly engages the nipple 117 as at 121. The eltir may be introduced into channel 119 through a tube Both channels 119 and 126 constitute transition zones whereby turbulent or non-laminar streams which are introduced into the respective channels are converted to laminar flow before they are discharged into the gap 115 where development desirably takes place under laminar flow conditions and mechanical deposition of development material as opposed to electrostatic deposition is thereby avoided.

In order to recover unused vacuum pick-up portion 105 is ment unit 22 with a fitting, as shown generally at 127, having a hollow interior 128. An extension of the curved surface of the fitting 127 is formed by an offset portion 130 which forms a vacuum slot 129 adjacent the end of the electrode area 104. The hollow interior 128 is communicated to the source of vacuum 50 by means of a conduit 131 connected to a tube 132 (FIGURE 1) which, in turn, is connected to the manifold 49.

In accordance with the principles of the present invention, it is contemplated that the electrode 112 be moved transversely relative to the path of movement of the photo-conductive surface 13. Thus, means are provided in accordance with this invention for continuously effecting a reciprocation of the electrode 112. To that end, the electrode 112 is considerably wider than the corresponding width of the main body member 106 as will be evident from an inspection of FIGURES 2 and 4.

particulate material, the provided in the develop- At opposite sides, the electrode 112 is provided with a coupling portion 133 and 134 respectively. One of the coupling portions 133 has connected thereto a spring 136 and is, in turn, connected to the end 137 of a pulley system including a pulley belt 138, the opposite end of which is connected to the coupling member 134 as at 139. A stop 155 is provided on each of the coupling portions 133, 134. The stops 155 limit the respective transverse movements of the electrode 112 when the stops 155 come into abutting engagement with the side surfaces of the main body member 106, as may be clearly seen in FIGURE 4.

In order to drivingly reciprocate the pulley belt 138, an electric drive motor is provided at 140 through a suitable driving connection including a crank arm 141 and a lever arm 142, a crank arm 143 is angularly reciprocated between a full line position and a dotted line position as illustrated in FIGURE 6, thereby angularly reciprocating a pulley wheel 144 over which the pulley belt 138 is trained. The respective runs of the pulley belt 138 are trained over direction changing pulley wheels shown in FIGURES 4 and 6 at 145, 146 and 147, the respective pulley wheels being carried by angularly disposed brackets 148 and 149, respectively.

As will be evident from an inspection of FIGURE 4, the electrode 112 is reciprocated transversely with respect to the direction of movement of the photo-conductive surface 13, thereby successively exposing the curved surface 104 of the electrode to a scrubbing action by the brushes 57 and 81. That action insures presentation of a clean electrode surface within the development area.

As will be evident from an inspection of FIGURE 5, the shroud forming the housing 89 around the brushes 57 and 81, respectively, have a special configuration which enhances the cleaning action. Thus, the housing 89 surrounding each respective brush is characterized by a narrow portion 89a in which the bristles of the brush 57 or the brush 81 are closely confined. The shroud -is then formed with an enlarged portion 89b which extends from a shoulder 150 to a bracket 151 at the lead edge of the electrode 112 identified at 152. In the enlarged portion 8912, the bristles snap out to full length. As the bristles come in contact with the curved surface 104 of the electrode 112, it will be noted that the curved surface 104 is spaced radially inwardly of the enlarged portion 89b, thereby to insure a good scrubbing contact with the bristles of the brush. At the trailing edge of the electrode 112, shown at 153, the bristles again extend to full length when they come in register with the vacuum pick-up area and particularly with an opening 154 incorporated in a scroll-shaped member 156 forming a part of the vacuum pick-up device 127.

Referring now to FIGURES 3 and 4, it will be noted that means are provided so that the development unit 22, including the electrode 112, be maintained at an optimum spacing dimension which may be within limits of approximately 50 to 500 microns. Although the invention may be practiced within the spacing limits just stated, it is desirable to reduce the gap dimension as much as possible, within physical limitations, to a lower limit fixed by the thickness of the selenium coating on the drum 11. We have found that the best results are obtained when the gap dimension is equal to the thickness of the selenium coating. Thus, the main body member of the electrode frame, indicated at 106, is carried on an adjustable micrometer sling shown generally at 157.

In the form of the invention shown in FIGURES 3 and 4, the micrometer sling 157 includes a first frame member 158 secured to the main body member 106 by fastening means 159 and projecting from the underside of the member 158 are two bosses 160 and 161 pivotally supporting from the bosses a subframe 162. A plurality of upstanding bosses are formed on the subframe 162 including a first boss 163 and a pair of second bosses 164 and 166. An ordinary pivot pin 167 extends between the bosses 161 and 163, however, the connection between the bosses 1'60 and 164, 166 includes not only a pin 168, but a stop member 169 and an adjustment screw 170 by means of which the relative positions of the main frame 158 and the subframe 162 may be adjusted in a direction transverse with respect to the rotational axis of the drum 11.

Below the subframe 162, a pair of rods 171 and 172 extend transversely between a mounting bracket 173 and 174 fastened to the main frame of the machine 10. An upper plate member 176 is grooved as at 177 and 178 for engagement and support on the upper surface of the rods 171 and 172. A clamping bracket 179 underlies the rods 171 and 172 and a clamping screw 180 extends through the clamping bracket 179 into engagement with the member 176.

The subframe member 162 has a downwardly projecting mounting post 181 closely received in a bearing sleeve 182 and the post 181 terminates in a flat abutment surface 183. A pilot pin spaced from the mounting post 181 is shown at 184 and enters a pilot opening 186 formed in the member 176 In order to effect vertical adjustment, a micrometer adjustment screw 187 is threadedly received in an apertured bight portion 188 of the sleeve 182 and an actuating knob 189 on the end of the adjustmeint screw 187 may be turned to vertically adjust the position of the micrometer sling, thereby adjusting the position of the electrode surface with respect to the photo-conductive surface of the drum. When a proper adjustment has been effected, a lock nut 190 may be tightened to permanently fix the position of adjustment. By virtue of such provision, the clearance between the electrode surface and the photoconductive surface may be controlled within limits of approximately 50 to 500 microns.

It is necessary to provide for synchronization of the speeds of drum 15 on which the document to be reproduced is mounted and the drum 11 so that the peripheral speed of the document being scanned in the optical system 17 is matched to the speed of the photo-conductive surface 13 takingin'to account the desired image reduction produced by the optical system 17. This may be accomplished by suitable drive connections between the drum 11 and the drum 15. Details of the drive connections are shown in FIGURES 1 and 6.

A pulley 191 is mounted on the document drum drive shaft 192. A pulley belt 193 is trained about the pulley 191 and another pulley 194 mounted on the shaft 196 for rotation therewith, all as seen in FIGURE 1. Shaft 196 is driven by a motor 197 through a series of driving connections provided by a pulley 109, a flexible belt 199, pulleys 200 and 201 on a common shaft 202, a belt 211 and a pulley 212 mounted on the shaft 196 for rotation therewith. Also mounted on shaft 196 for rotation therewith is a pulley 213 which drives the drum 11 mounted on the shaft 12 through intermediate driving elements consisting of a flexible belt 215 and a pulley 216 mounted on the shaft 12. As is evident, the proper relative speeds of the drum 15 and the drum 11 can be fixed by selecting suitable sizes for the various pulley elements above described and can be varied as required for different image reductions desired by providing interchangeable pulley sizes.

Adjustments of the tension of the belt 211 is also provided for. Idle pulleys 217 are mounted for rotation on the bracket 218 which is adjustably mounted on a housing or frame member 219 as may be convenient, by means of bolts 220 inserted through elongated holes 221 and threaded into apertures in the housing or frame member 219. Thus, the tension of the belt 199 may be adjusted by moving the bracket 218 towards or away from the pulley 212 and locking the bracket 218 in place by tightening the bolts 220. A similar adjust-able bracket mounting 222 for idle pulleys 223 is provided for the flexible belt 215 and the operation thereof should be readily understood without it being necessary to repeat the details.

In operation, the entire process is carried out in a continuous manner. Thus, the dum 11 may be rotated in a counterclockwise direction, using the orientation of FIG- URE 1, and the photo-conductive surface 13 will be successively uniformly charged by the corona charging device 16 and exposed when positioned oppositely the optical system 17 and then developed in the development unit 22.

Multiple layers of fluid are interposed in the development zone between the development unit 22 and the photo-conductive surface 13. In this connection, the two channels 119 and 126, respectively, carry streams of air and the channel 126 functions as a carrier stream to interpose a fluid layer containing developer powder into the development zone between the electrode 112 and the photo-conductive surface 13. A stream of clean air discharged from the channel 119 will prevent the developer powder from leaving the electrode area. The extremely close clearance relation between the side sealing rings 207 and 208 and the curved surface 104 of the electrode 112 will confine the developer powder in the developer zone. Because of the latent electrostatic image on surface 13, the developer powder is attracted to the image areas, thereby rendering the image visible and utilitarian, whereupon the image is then transferred to the surface of the film 23 by pressure contact regulated by the actuator means 28. Unused particulate material is recovered through a vacuum slot 129 and is removed from the situs through the vacuum collection system. The photoconductive surface 13 is cleaned by the brush 39, thereby conditioning the photo-conductive surface 13 for a new cycle.

During the course of operation, the electrode 112 is cyclically reciprocated so that the curved surface 104 moves transversely with respect to the path of movement of the photo-conductive surface 13 and the curved surface 104 is cleaned continuously by the brushes 57 and 81.

By virtue of the micrometer sling support of the development unit 22, the position of the electrode 112 with respect to the photo-conductive surface 13 may be closely regulated within 50 to 500 microns, thereby insuring an optimum spacing relation for effective image reproduction. Particles removed by the brushes 57 and 81 are removed from the situs by the vacuum pick-up acting through the conduits 92 and 93.

Although minor modifications might be suggested by those versed in the art, it should be understood that we Wish to embody within the scope of the patent warranted hereon all such modifications as reasonably come within the scope of our contribution to the art.

We claim as our invention: 1. Electrostatographic apparatus comprising a rotatable drum having radial side walls in spaced parallel relationship and a circumferentially continuous peripheral surface of photoconductive material on said drum,

said drum having a sealing disk on each said radial side wall made of insulator material to prevent ions from running out to the edges of said peripheral surface. 2. Electrostatographic apparatus as defined in claim 1 and development means comprising an electrode forming a surface spaced within 0.0005

inch of said sealing disks. 3. Electrostatographic apparatus as defined in claim 2 and further characterized by said development means including means mounting said electrode to reciprocate transversely with respect to said peripheral surface and in a direction generally parallel to the rotational axis of the drum. 4. Electrostatographic apparatus as defined in claim 3 and further characterized by said development means including means to How a laminar stream of developer material between said electrode and said peripheral surface of said drum. 5. Electrostatographic apparatus as defined in claim 4 and further characterized by brush means on opposite sides of said drum to scrub the electrode surface. 6. Electrostatographic apparatus as defined in claim 5 and further characterized by mounting means for said development means including a micrometer sling for adjusting said electrode towards and away from said peripheral surface of said drum to maintain an optimum spacing adjustment between the adjoining surfaces in the order of about 0.003 to 0.008 inch.

References Cited UNITED STATES PATENTS 3,190,199 6/1965 Clark 1.7 3,330,683 7/1967 Simm ll7--37 3,331,355- 7/1967 Donalies 118637 2,033,290 3/1936 Landrock 88--24 3,221,621 12/1965 Cranskens 95-1.7

JOHN M. HORAN, Primary Examiner.

11.8. C1. X.R.

and r p y 118-637 

1. ELECTROSTATOGRAPHIC APPARATUS COMPRISING A ROTATABLE DRUM HAVING RADIAL SIDE WALLS IN SPACED PARALLEL RELATIONSHIP AND A CIRCUMFERENTIALLY CONTINUOUS PERIPHERAL SURFACE OF PHOTOCONDUCTIVE MATERIAL ON SAID DRUM, SAID DRUM HAVING A SEALING DISK ON EACH SAID RADIAL SIDE WALL MADE OF INSULATOR MATERIAL TO PREVENT 